Subject

Chemistry

The science of atoms, reactions and materials, from your first fizzing experiment to university-level theory.

Chemistry starts with atoms and the periodic table and moves through bonding, reactions, moles, acids and bases, redox, electrolysis, energetics, rates, equilibria and organic chemistry.

The moles unit is the pivot point of the whole subject. Before it, chemistry is largely descriptive. After it, chemistry becomes quantitative and you can calculate what a reaction will produce. Learners who find chemistry suddenly hard have usually arrived at moles without securing the atoms and bonding units first.

Chemistry is the level at which materials stop being a list of substances and start being a system you can reason about. Cooking, medicine, corrosion, batteries and the atmosphere are all the same subject.

Units: 18
Steps: 344
Questions: 2,060

Who this track is for

Introductory through to A-level and first-year undergraduate chemistry.

How to approach it

Secure atoms, bonding and the periodic table before attempting moles
Write out reaction equations by hand rather than reading them
Organic chemistry is pattern recognition, so volume of practice pays off

Study guide · 9 min readHow to Learn ChemistryChemistry is the subject people most often try to memorise and most reliably should not. A practical guide to the order that works, why bonding is the hinge the whole subject turns on, and what to do when the calculations stop making sense.

What you will be able to do

Predict how an element behaves from its position in the periodic table
Balance an equation and say why the balancing is not optional
Explain why strong and concentrated are different properties of an acid
Say what a catalyst does and, more usefully, what it does not do

The thing people get wrong

That chemistry is about memorising reactions. Almost every reaction in the track follows from electron arrangement, and a student who understands bonding can predict far more than one who has memorised a list.

If you only do 3 units

Nothing later in chemistry makes sense without these three, and everything later makes considerably more sense with them. They are the whole foundation of the subject in about sixty short steps.

What the questions look like

8 real questions from across the Chemistry track, easiest first, each with the answer and the reason behind it. Every unit page below has thirty more.

Fill the blankLevel 1
1. In the modern periodic table, elements are arranged in order of increasing ____ number.
- atomiccorrect
- mass
- neutron
- shell
Elements are ordered by atomic number, which increases by one from each element to the next.
Multiple choiceLevel 1
2. Which element does the chemical symbol 'O' represent?
- Oxygencorrect
- Osmium
- Gold
- Oxide
The symbol O stands for oxygen.
Fact or fibLevel 1
3. A gas will spread out to fill any container it is placed in.
Answer: True
Gas particles move freely and spread to fill all the available space.
Multiple choiceLevel 1
4. A covalent bond forms when...
- Two non-metal atoms share a pair of electronscorrect
- A metal gives its electrons to a non-metal
- Two metal atoms pool their electrons
- Atoms lose all of their electrons
Covalent bonds are shared pairs of electrons between non-metal atoms.
Fill the blankLevel 1
5. A solution with a pH lower than 7 is called an ____.
- Acidcorrect
- Base
- Salt
- Alkali
Solutions below pH 7 are acidic.
Fill the blankLevel 1
6. Equations must be balanced because atoms are never created or destroyed, which is the law of conservation of ____.
- masscorrect
- charge
- energy
- volume
The law of conservation of mass means the number of each type of atom stays the same.
Fill the blankLevel 1
7. The acid found in vinegar is ____ acid.
- ethanoiccorrect
- citric
- sulfuric
- carbonic
Vinegar is a dilute solution of ethanoic acid (also called acetic acid).
Build the sentenceLevel 2
8. Build the rule for combining two half-equations into an overall equation.
Answer: multiply each half-equation so the electrons cancel
The electrons lost must equal the electrons gained, so you scale each half-equation until the electrons cancel.

Units in Chemistry

Listed in the order they are meant to be worked through.

Practise Chemistry

2,060 questions, in tiny sessions you can finish in a few minutes.

Start playing

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.